This invention relates to burners and, more specifically, to gas burners suitable for use in appliances and the like.
Burners are used, for example, in apparatuses including furnaces and appliances such as clothes dryers. A principle component of burners is a nozzle typically in the form of a venturi tube. Combustible gas is fed into the nozzle and entrains air into the nozzle. The air and gas is mixed in the venturi and the mixture emerges from the outlet end. An igniter may be attached directly to the venturi tube in front of the outlet opening in alignment with a longitudinal axis along which the nozzle extends and ignites the mixture as it leaves the outlet, thereby creating flame which produces heat that is utilized by the apparatus.
In furnaces, a plurality of burner nozzles are typically arranged side-by-side and are designed for cross-ignition of the gas in adjacent nozzles. One conventional nozzle has two plenum chambers located at an outlet end of the venturi tube. Each plenum chamber has a thin outlet slit along its side edges. Flame released from the side outlet slits of one nozzle ignites gas from an adjacent nozzle.
Clothes dryer burners are horizontally fired into ducts of the dryer. The ducts shield the open flame and force the heated gases in the desired direction. The burner may include an attachment known as a flame spreader which is separately formed from the nozzle, mounted such as by welding to the nozzle and axially spaced from the outlet opening of the nozzle. One function of a flame spreader is to prevent upward lifting or curling of the flame as it travels horizontally. The flame spreaders are disposed in the flame and thus, are exposed to relatively high temperatures. This requires the flame spreaders to be fabricated from metals or coated with materials which can withstand this high temperature environment.
Conventional gas dryer burner nozzles typically produce flame having a length of, for example, about one foot. However, space is limited in the dryer. Long flame lengths may result in inefficient heat transfer between the flame and air inside the duct work, overheating of the duct work, or an increase in the cost of the dryer due to the use of enough duct work to accommodate the long flame. Heated gases from the horizontal flame are typically directed through a 90xc2x0 elbow, generally vertically to another 90xc2x0 elbow, through a screen and then into a rotatable drum in which clothes are dried.
Typical gas dryer burner nozzles can be difficult and relatively expensive to manufacture. Such burner nozzles are fabricated by a practice of forming a venturi tube from tubing and welding a stamped flame spreader to an end of the formed burner tube.
The present invention is directed to a burner nozzle for producing a shaped and/or shortened flame for efficient heat transfer. The burner is characterized by a curved head with an imperforate portion for shaping the flame. The burner is particularly well suited for use in clothes dryers where a flame that is spread out transverse to the direction of gas flow and that has a reduced length, is desired. A burner nozzle produced in accordance with the present invention reduces the fabrication costs and results in efficient heat transfer.
In general, the invention is a burner nozzle that includes a burner tube that extends along a central axis and has an inlet end portion for receiving combustible gas and air and an outlet end portion for releasing a mixture of the gas and air. A main gas flow passage extends along the central axis between the inlet end portion and the outlet end portion. A curved head that has a plurality of openings is connected to the outlet end portion. The curved head includes an imperforate portion that is disposed near the central axis. The plurality of openings and imperforate portion of the curved head create a transverse flow of the mixture of gas and air out of the curved head to produce a shaped flame that results in efficient heat transfer between the flame and air inside a heat-receiving member, such a duct, located downstream of the outlet end.
As to the specific features of the burner nozzle, the burner tube may include wing portions that extend laterally from the burner tube for attachment to the duct of a dryer. The curved head may comprise a curved portion defined by a portion of a sphere, a cylindrical portion that extends from said curved portion and a mounting flange that extends transversely from said cylindrical portion.
The curved head may be hemispherical in shape with round openings evenly spaced about the circumference of the curved head. The plurality of openings in the curved head may be arranged in two rows. The holes of the first row are circumferentially spaced around the head near a base of the head. The holes of the second row are circumferentially spaced around the head between the first row of openings and a tip of the burner located at the central axis. The openings of the first row near the base of the curved head may be larger than the openings of the second row that are between the first row and the tip. The head may also include a central opening at the tip, along the central axis.
A burner assembly may be formed by fastening the inventive burner nozzle in the interior of a combustion tube. The combustion tube may be comprised of two articles formed of stamped metal or a single rolled form. Preferably, in the case of a clothes dryer application, only a single burner nozzle is used in the burner assembly. The heat receiving member or duct comprises a passageway having a portion with a shape (e.g., circular) that corresponds to the elongated shape of the flame.
A portion of the mixture of gas and air may be passed through an opening in the head that encompasses the central axis. The diameter of the opening that encompasses the central axis can be varied to elongate or shorten the length of the flame.
A general method of producing a shaped flame from a burner nozzle comprises directing combustible gas and air into an inlet end portion of a burner tube that extends along a central axis. The gas and air are mixed in the burner tube. The gas and air are directed along the central axis toward and outlet end portion of the burner. A portion of the gas and air are diverted by an imperforate portion of a curved shaped head at the outlet end portion away from the central axis. The gas and air are passed through circumferentially spaced openings in the curved head. The mixture is ignited to produce a shaped flame. When the gas and air are passed through the circumferentially spaced openings, the head may direct a portion of the gas and air in a direction that is transverse to the central axis.
The present invention offers numerous advantages over prior gas dryer burners. The imperforate portion in conjunction with the openings in the curved head enable elongation of the flame transverse to the central axis of the burner nozzle. This results in a flame that has an ideal shape when used with duct work having a corresponding passageway (e.g., a circular duct). There is an efficient heat transfer between the elongated transverse flame and the air in the duct since there is less wasted space compared to the use of a burner that produces a flame with a small diameter in a duct that has a large diameter. Alternatively, or in addition to the flame shaping feature, the burner nozzle may produce a shortened flame having a length of, for example, about one half of conventional burner nozzles used in clothes dryers. In vertical firing applications there is a shorter distance between the end of the flame and the entry to the drum than in horizontal firing applications. Therefore, a flame that is too long may overheat the duct work, the screen or articles in the dryer.
Other embodiments of the invention are contemplated to provide particular features and structural variance of the basic elements. The specific embodiments referred to, as well as possible variations in the various features and advantages of the invention, will become better understood from the accompanying drawings together with the detailed description that follows.